package com.novel.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.novel.dto.Result;
import com.novel.entity.Shop;
import com.novel.mapper.ShopMapper;
import com.novel.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.novel.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import static com.novel.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    private static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(2, 3, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue<>(1));
    }

    @Override
    public Result queryById(Long id) {
        //缓存穿透
        Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
        //Shop shop = queryWithLogicalExpire(id);

        if(shop == null){
            return Result.fail("店铺不存在");
        }
        //7.返回
        return Result.ok(shop);
    }

    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中的是否为空值
        if(shopJson != null){
            return null;
        }
        //4.不存在，根据id查询数据库
        Shop shop = getById(id);
        //5.不存在，返回错误
        if(shop == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }

    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中的是否为空值
        if(shopJson != null){
            return null;
        }
        //4.不存在，根据id查询数据库
        //获取互斥锁
        String lockKey = "lock:shop:" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            if(!isLock){
                Thread.sleep(50);
                return queryWithPassThrough(id);
            }
            //获取锁之后再次查询缓存是否存在
            String shopJsonTwo = stringRedisTemplate.opsForValue().get(key);
            if(StrUtil.isNotBlank(shopJsonTwo)){
                //3.存在，直接返回
                unLock(lockKey);
                return JSONUtil.toBean(shopJsonTwo, Shop.class);
            }
            shop = getById(id);
            //5.不存在，返回错误
            if(shop == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //6.存在，写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //释放互斥锁
            unLock(lockKey);
        }

        //7.返回
        return shop;
    }

    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)){
            //3.不存在，直接返回
            return null;
        }
        //命中，把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            return shop;
        }

        //获取互斥锁
        String lockKey = "lock:shop:" + id;
        boolean isLock = tryLock(lockKey);
        if (isLock) {
            //开启一个线程去重建缓存
            newCachedThreadPool().execute(() -> {
                try {
                    //重建缓存
                    Shop shop1 = getById(id);
                    RedisData redisData1 = new RedisData();
                    redisData1.setExpireTime(LocalDateTime.now().plusSeconds(30L));
                    redisData1.setData(shop1);
                    stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData1));
                } catch (Exception e) {
                    throw new RuntimeException();
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }

        //7.返回
        return shop;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id == null){
            return Result.fail("店铺id不能为空");
        }
        //更新数据库
        updateById(shop);
        //删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
